In recent years, production of a full color print can be achieved via the electrophotography system using the toner for electrostatic charge image development (hereinafter it is called as an electrophotographic toner or simply a toner) in addition to a monochrome print which is most representative for a document print. Since such full color image forming apparatus can produce a required number of prints on demand without preparing a printing plate for a usual printing process, it is increasingly used in a small volume printing field having many opportunities of small-quantity print order (for example, refer to Patent Document 1).
In producing a full color print, such as a catalog and an advertisement print, with a toner, the toner used is required to produce an image which exhibits a faithful color reproduction to the original. In full color image formation, yellow, magenta and cyan color toners each are superimposed to reproduce a target color image. In order to realize faithful color reproduction, it was required for the color toners to improve the color reproduction property.
Therefore, investigation of various colorants has so far been made for the purpose of improving the color reproduction of a color toner.
An example of typical magenta colorants for color toners is a quinacridone pigment. The toner incorporating a quinacridone pigment has outstanding light resistance and has a preferable magenta toner, therefore, a quinacridone pigment is used for general-purpose. However, this quinacridone pigment has a problem of dispersibility and the toner incorporating a quinacridone pigment tends to produce a turbid color at the time of a color pile. It is difficult to satisfy the request to produce a print of the image of the computer graphics or the high saturation display which are becoming highly required in recent years.
Instead of using solely a quinacridone pigment, the system in which other dye is added to a quinacridone pigment is known in order to increase color saturation (for example, refer to Patent Document 1). Furthermore, the proposal is made also about the system which uses a combination of a quinacridone pigment and a naphthol pigment (for example, refer to Patent Document 2).
Moreover, it is also known the combined use with an anthraquinone pigment (for example, refer to Patent Document 3).
However, all of these proposed systems are inferior in light resistance to the system solely using a quinacridone pigment which exhibits high light resistance as a magenta pigment. They had a problem which cannot keep the color stable when the print is used over a long period of time.
Furthermore, in order to form an image with higher color saturation, a proposal is made in which the toner incorporating the coloring matter composed of a metallic compound and a dye (for example, Patent Document 4).
However, it is difficult to secure a large color region because, even if a certain specific color region is expanded and color saturation is increased, color saturation balances tend to be lowered. Especially, when color reproduction according to a display was performed, there occurs a problem that only a specific color region is approaching to the color reproduction range of sRGB used as a standard made by IEC (International Electrotechnical Commission) in October 1998), and color reproduction in all of the color regions cannot be performed.
Patent Document 1: Unexamined Japanese patent application publication (hereafter it is called as JP-A) 2007-286148
Patent Document 2: JP-A 2006-267741
Patent Document 3: JP-A 2006-154363
Patent Document 4: JP-A 2007-316591